Form and function of the gastropod larval nervous system

Many of the world's most abundant organisms depend critically upon larval stages that are poorly understood in terms of their form and function. The seas are full of such invertebrate larvae, which permit dispersal and thus ensure replenishment of populations, continued genetic diversity and colonisation of novel geographic regions. Such larval forms are essential for economically important species in the wild and present challenges during aquaculture. From the perspective of fundamental biological principles, understanding larval stages is also essential for explaining the development of subsequent adult body plans and the evolution of the very biodiversity upon which the world relies. Our lab, together with only a handful of others worldwide, has recently made major inroads in describing the form and function of larvae of one of the most important phyla of marine organisms: the molluscs. In this application, we propose to examine how the larval nervous system controls the cilia and muscles used to generate swimming and feeding behaviours in the common intertidal snail, Ilyanassa. We will start by using techniques which have already proven useful in our hands (immunocytochemistry , behavioural pharmacology) to identify neurotransmitters in the nevous system and determine their roles. However, to understand the functions of individual neurons, we will need to use electrophysiology, coupled with modern optical imaging techniques. These studies will involve the use of microelectrodes to impale single larval neurons, which can be visualized with vital stains or DIC optics, and will permit the study of cellular characteristics and synaptic connections. Simultaneous dye injections will reveal detailed anatomy. We will also turn to state-of-the-art optical imaging techniques which will permit us to study activity of both single neurons and populations of cells. These studies will comprise the first detailed analyses of the larval nervous system of molluscs at the cellular level and provide a basis for future comparisons across the molluscs and between phyla.